Geuloyij of the JJuviiioad Creek Area. 345 



of brecciation, as is well seen in a section between the mine and the 

 Diamond Creek station. The dyke in this section is seen to be 

 bounded \)\ ciuiiipled slates, and the brecciated zone occurs seven 

 or eight i'eet to the west. The width of the original fracture zone 

 is probably not represented by the width of the dyke. Lateral pres- 

 sure exerted during intrusion and a certain amount of stoping 

 has probably enlarged the width of the fracture. It is not clear 

 what the final displacement is, but it is probable that the movement 

 was oscillatory, and the hnal displacement may have been small. 

 If the quartz reefs on either side of the dyke at the stii-face are 

 identical no great displacement can have occurred. 



(c) Tlic JJidinoitd Creek dijke. 



ilie dyke near the mine strikes practically north and south, and 

 dips to the east at about 45 deg., i.e., the dip is approximately at 

 right angles to the dip of the shales. In some places the dip is 

 nearly vertical and in others it is much flatter than the average. 

 Considerable variation occurs in the width of the dyke, both along 

 its length, and in vertical sections. The maximium widtli 

 is about 35 feet, and the average about 20 feet. Rectangular 

 jointing, with one set of joints roughly parallel to the dip of the 

 dyke, and the other set almost at right angles to these, frequently 

 occurs. Slickensides, striae, brecciation and other evidence of 

 movement under pi-essure are not uncommon, especially near the 

 faults. Large horizontal slickensides occur in the dyke below 

 the 300 feet level north, and large curved ones are not infrequently 

 present in other parts of the mine. Lnpregnation with pyrites of 

 the bi-eccia and slates surrounding the dyke for a few feet has taken 

 place. 



(d) Faulting later than the intrusion of the dyke. 



The best opportunity for studying this faulting was afforded at 

 the mine. Nearly all these faults appear to be normal strike 

 faults having a strike approximately north 20 deg. east, and 

 hading to the west. Their strike varies from north 10 deg. east to 

 about north 30 deg. east, and their hade is generally between the 

 limits 40 deg. and 80 deg. The effect of the difference in strike 

 of the faults and the dyke gives the faults the appearance of pitch- 

 ing to the north. Being normal faults, the dyke is always brought 

 back in a westerly direction, and this has materially aided the com- 

 pany in the lower levels, where the dyke was going away from the 

 shaft. In the Union mine, immediately to the south of the Diamond 



